The present invention relates to insulating glass units and, more particularly, to a method and apparatus for applying adhesive and desiccant to spacer assemblies used in constructing insulating glass units.
Insulating glass units (IGU""s) are used in windows to reduce heat loss from building interiors during cold weather or to reduce heat gain in building interiors during hot weather. IGU""s are typically formed by a spacer assembly that is sandwiched between glass lites. The spacer assembly usually comprises a frame structure that extends peripherally around the unit, an adhesive material that adheres the glass lites to opposite sides of the frame structure, and desiccant in an interior region of the frame structure for absorbing atmospheric moisture within the IGU. The glass lites are flush with or extend slightly outwardly from the spacer assembly. The adhesive is disposed on opposite outer sides of the frame structure about the frame structure periphery, so that the spacer is hermetically sealed to the glass lites. An outer frame surface that defines the spacer periphery may also be coated with sealant, which increases the rigidity of the frame and acts as a moisture barrier.
One type of spacer construction employs a U-shaped, roll formed aluminum or steel elements connected at its end to form a square or rectangular spacer frame. Opposite sides of the frame are covered with an adhesive (e.g., a hot melt material) for securing the frame to the glass lites. The adhesive provides a barrier between atmospheric air and the IGU interior which blocks entry of atmospheric water vapor. Desiccant is deposited in an interior region of the U-shaped frame element. The desiccant is in communication with the air trapped in the IGU interior and removes any entrapped water vapor and thus impedes water vapor from condensing within the IGU. After the water vapor entrapped in the IGU is removed, internal condensation only occurs when the seal between the spacer assembly and the glass lites fails or the glass lites are cracked.
Prior art systems for applying adhesive to outer surfaces of a U-shaped spacer and desiccant to an inner region of the U-shaped spacer are pressure-based systems. Desiccant or adhesive under pressure is supplied from a bulk supply, such as a 55-gallon drum by a piston driven pump. The pressure of the desiccant or adhesive supplied by the piston driven pump is approximately 3500 psi. A hose delivers the desiccant or adhesive in response to actuation of the piston driven pump to an inlet of a compensator. The compensator allows a user to select a desired pressure that will be provided at the outlet of the compensator. Typically, the output from the compensator is between 800 and 1200 psi. When the pressure at the outlet of the compensator is less than the selected pressure, the desiccant or adhesive material under pressure supplied to the inlet of the compensator causes the piston to move from a xe2x80x9cclosedxe2x80x9d position to an xe2x80x9copenxe2x80x9d position. Movement of the compensator piston to the xe2x80x9copenxe2x80x9d position allows the material under pressure supplied to the compensator inlet to flow toward the outlet until the pressure at the outlet reaches the selected pressure. When the pressure at the outlet reaches or slightly exceeds the selected pressure, the material under pressure at the outlet of the compensator forces the piston back to the xe2x80x9cclosedxe2x80x9d position, stopping material flow from the compensator inlet to the outlet.
The prior art system includes needle valves that dispense the material into contact with the spacer frame. The needle valves are adjustable by the user to control the flow rate of the desiccant or adhesive. The flow of the desiccant or adhesive material is determined by the orifice size, viscosity and pressure of the material. The pressure of the adhesive or desiccant material is dependent on several variables, including viscosity, temperature, nozzle size, and batch to batch variations of the dispensed material. Because so many variables are involved, the amount of desiccant or adhesive dispensed is subject to a fairly wide fluctuation due to pressure changes that are attributable to various factors mentioned above.
Pressure-based systems require the operator to constantly adjust for flow. Often, an excessive amount of material is dispensed to ensure that under all conditions an adequate amount of material is applied to the spacer frame. If the dispensing system is down for more than a few minutes, the system has to be purged due to an increased viscosity of the desiccant or adhesive that has cooled. The increased viscosity of the material that has been allowed to cool makes it difficult to pass the material through the nozzle and flow material through the system.
The present invention concerns a system for controlled dispensing of a material onto an elongated window component. The system includes a dispensing nozzle, a conveyor, a metering pump, a pressurized bulk supply, and a controller. The nozzle is adapted to dispense material into contact with one or more surfaces of the elongated window component when the window component is at a delivery site located along a path of travel of the elongated window component. The conveyor moves the elongated window component along the path of travel with respect to the nozzle at a controlled rate of speed. The metering pump delivers controlled amounts of the material to the nozzle. The pressurized bulk supply delivers the material to an inlet of the metering pump. The controller regulates the speed of the metering pump to control the flow rate of the dispensed material.
In one embodiment, a pressure transducer monitors the pressure of the material before the material is dispensed from the nozzle. The pressure transducer may be positioned for monitoring pressure at an inlet side of the metering pump. The controller regulates pressure of the material delivered to the metering pump from the bulk supply based on the pressure monitored by the pressure transducer. In this embodiment, the controller includes an output coupled to the bulk supply for adjusting the pressure of the material to minimize a pressure drop between the inlet of the metering pump and the outlet of the metering pump.
One embodiment of the invention is configured to dispense material onto one or more surfaces of a generally U-shaped spacer frame member. In this embodiment, a first nozzle is adapted to dispense desiccant into an interior of the U-shaped spacer frame and a second nozzle is adapted to deliver an adhesive onto an outer surface of the spacer frame. One variation of this embodiment includes three nozzles for delivering adhesive to three outer sides of the U-shaped spacer frame. In another variation of this embodiment one type of material is delivered to the sides of the elongated member by two side nozzles and a different material is applied to the bottom of the member by a third nozzle. This practice is commonly referred to as xe2x80x9cco-extruding.xe2x80x9d
In one embodiment, the metering pump is a gear pump. In one embodiment an optic sensor is included for monitoring movement of the elongated window component along the conveyor. The optical sensor may be coupled to the controller which initiates dispensing of the material through the nozzle onto the elongated window component based on sensed movement of the elongated window component by the optical sensor.
In one embodiment, the elongated window component is a spacer frame and member having a gas bleed hole at a location along the length of the spacer frame. The controller and optical sensor sense a presence of the gas bleed hole and stop dispensing material in a region of the gas bleed hole as the spacer moves along the travel path past a dispensing nozzle. The controller may include a computer interface that allows a user to program parameters relating to dispensing of the material onto the elongated window component. One such parameter that the computer interface allows a user to program is a width of the elongated window component. The controller responds to an entered width parameter by adjusting the controlled amounts of material delivered by the metering pump.
The present invention allows material to be dispensed along a length of an elongated window component in a controlled manner. The elongated window component is moved along the path of travel relative to a material dispensing nozzle at a controlled speed. Material from a bulk supply is delivered to an inlet of a metering pump. The metering pump has an outlet coupled to the nozzle to dispense the material through the nozzle into contact with a surface of the elongated window component. Pressure of the material is monitored with the pressure transducer before the material is dispensed from the nozzle.
The speed of the metering pump is regulated to control the rate of flow of the dispensed material from the nozzle. In one embodiment, pressure of the material delivered to the metering pump from the bulk supply is regulated based on a pressure sensed by the pressure transducer.
In an embodiment, wherein the metering pump is a gear pump, a speed of rotation of the gear pump is controlled to meter controlled amounts of material onto the elongated window component. Dispensing of material from the nozzle may be periodically stopped as a plurality of elongated window components move along a path of travel past the nozzle. Dispensing of material may also be stopped to leave openings along the length of the frames uncovered.
A system for controlled dispensing constructed in accordance with the present invention has several advantages over pressure-based dispensers. The present system is much less sensitive to material viscosity variations that exist between material suppliers and batch-to-batch inconsistencies. The system of the present invention does not require operator adjustments due to temperature and system pressure fluctuations that occur over time. The system of the present invention dispenses precise amounts of desiccant and adhesive. Spacer, desiccant and adhesive waste is greatly reduced during start-up and shutdown periods. Use of the metering pump reduces the effect of pressure spikes from the bulk supply.
Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description in connection with the accompanying drawings.